server unexpectedly closed network connection

Hello, We are trying to transmit a file from us to the bank. Most of the time the transmission works. According to the bank's review of our log, they say we sometimes don't get past the usersname/password. Here are the sections of the log that shows when WinSCP works and when it fails. I also included the WinSCP script. We plan to put WireShark on the server transmitting from us to the bank. Aslo, we see no issues with the firewall. We're using SFTP (FTP over SSH). The bank is using Maverick SSHD.